Consistent appraisals of homes and businesses outfitted with photovoltaic (PV) installations are a real challenge for the nation’s real estate industry, but a new tool developed by Sandia National Laboratories and Solar Power Electric™ and licensed by Sandia addresses that issue. Sandia scientists, in partnership with Jamie Johnson of Solar Power Electric™, have developed PV ValueTM, an electronic form to standardize appraisals. Funded by the Department of Energy’s Office of Energy Efficiency and Renewable Energy, the tool will provide appraisers, real estate agents and mortgage underwriters with more accurate values for PV systems.

The tool uses an Excel spreadsheet, tied to real-time lending information and market fluctuations, to determine the worth of a PV system. An appraiser enters variables like ZIP code, the system size in watts, the derate factor – which takes into account shading and other factors that affect a system’s output – tracking, tilt and azimuth, along with a few other factors, and the spreadsheet returns the value of the system as a function of a pre-determined risk spread. The solar resource calculation in the spreadsheet is based on the PVWattsTM simulator developed by the National Renewable Energy Laboratory, which allows the spreadsheet to value a PV system anywhere in the U.S.

“With PV Value™, appraisers can quickly calculate the present value of energy that a PV system can be estimated to produce during its remaining useful lifetime, similar to the appraisal industry’s income approach,” said Johnson. “Additionally, a property owner thinking about installing PV can now estimate the remaining present value of energy for their future PV system and what it could be worth to a purchaser of their property at any point in time in the event a sale of the property takes place before the estimated payback date is reached.”